Review of GlueX FCAL Design Richard Jones, University of Connecticut GlueX collaboration meetingSept , Newport News as presented by Scott Teige, Indiana University reviewed by

Richard Jones, GlueX meeting, Newport News, September 9-11, Review Issues Performance measured by Radphi Performance measured by Radphi energy resolution energy resolution spatial resolution spatial resolution minimum cluster separation minimum cluster separation sensitivity to charged tracks sensitivity to charged tracks electromagnetic background effects electromagnetic background effects State of the Monte Carlo simulation State of the Monte Carlo simulation comparison of expected, measured resolution comparison of expected, measured resolution design issues affecting photon yield design issues affecting photon yield efficiency of the reconstruction efficiency of the reconstruction

Richard Jones, GlueX meeting, Newport News, September 9-11, The Radphi Apparatus photon beam lead glass detector beryllium target barrel Pb-SciFi calorimeter

Richard Jones, GlueX meeting, Newport News, September 9-11,

5 Performance: energy resolution based on widths of p 0 and h based on widths of p 0 and h h width mainly d E h width mainly d E p 0 width equally d E and dq p 0 width equally d E and dq best fit to data: best fit to data: GlueX value: GlueX value:

Richard Jones, GlueX meeting, Newport News, September 9-11, Performance: spatial resolution based on width of p 0 based on width of p 0 h width determines d E h width determines d E p 0 width determines dq p 0 width determines dq best fit to data: best fit to data: GlueX value: GlueX value:

Richard Jones, GlueX meeting, Newport News, September 9-11, Performance: cluster separation reconstruction tuned to reconstruction tuned to minimize split-offs minimize split-offs maximize separation maximize separation best compromise: best compromise: e ~ 50% at 6 cm e ~ 50% at 6 cm e -> 0 at 4 cm e -> 0 at 4 cm depends on energy depends on energy

Richard Jones, GlueX meeting, Newport News, September 9-11, Performance: charged hits charged pions make clusters charged pions make clusters by charge exchange by charge exchange by nuclear absorption by nuclear absorption typical energy 200 MeV typical energy 200 MeV dominate high-multiplicity sample before cp veto dominate high-multiplicity sample before cp veto effects on calorimetry: effects on calorimetry: occupy space occupy space odd-shaped clusters odd-shaped clusters affects computation of neutral energy in the trigger affects computation of neutral energy in the trigger before cp veto

Richard Jones, GlueX meeting, Newport News, September 9-11, Performance: E-M background EM backgrounds about the same for Radphi, GlueX EM backgrounds about the same for Radphi, GlueX Around the beam hole Around the beam hole higher rates higher rates harder spectrum harder spectrum no sharp cutoff in r no sharp cutoff in r effects on calorimetry: effects on calorimetry: degrades resolution degrades resolution extra small-r clusters extra small-r clusters radiation damage takes place over time radiation damage takes place over time response depressed by radiation damage ADC threshold 15 MeV

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: comparison

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: comparison

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: comparison

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: comparison

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: light yield depression at normal incidence? better resolution with leakage?

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: light yield depression at normal incidence? depression at normal incidence? not severe: most shower tracks are randomized not severe: most shower tracks are randomized shower core preferentially suppressed shower core preferentially suppressed for perfect blocks “hole” is ±15º for perfect blocks “hole” is ±15º contributes extra fluctuations in light yield contributes extra fluctuations in light yield design issue: optical coupling between glass and PMT design issue: optical coupling between glass and PMT air gap phototube qCqC total internal reflection coaxial shower particle

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: light yield better resolution with leakage? better resolution with leakage? showers fluctuate in depth by 1 X 0 showers fluctuate in depth by 1 X 0 attenuation effects: attenuation effects: late-forming showers have higher yields late-forming showers have higher yields leakage effects: leakage effects: late-forming showers have higher losses from leakage late-forming showers have higher losses from leakage competition between attenuation and leakage ! competition between attenuation and leakage ! There is an ideal depth for a lead-glass calorimeter which depends on energy scale. There is an ideal depth for a lead-glass calorimeter which depends on energy scale. for GlueX design, attenuation dominates for GlueX design, attenuation dominates design issue: optical properties of wrapping around blocks design issue: optical properties of wrapping around blocks

Richard Jones, GlueX meeting, Newport News, September 9-11, Simulation: reconstruction efficiency must be included for realistic acceptance must be included for realistic acceptance For Radphi, efficiency is 89% per photon in the final state for exclusive all-neutral channels, counting only photons that hit the lead-glass detector in the “strike zone”. For Radphi, efficiency is 89% per photon in the final state for exclusive all-neutral channels, counting only photons that hit the lead-glass detector in the “strike zone”. should be better for GlueX than for Radphi should be better for GlueX than for Radphi Radphi showers are twice as far from normal incidence Radphi showers are twice as far from normal incidence showers leak out the side of the detector showers leak out the side of the detector centroid resolution is degraded by depth fluctuations centroid resolution is degraded by depth fluctuations GlueX showers are better resolved by a spatial factor of ~3 GlueX showers are better resolved by a spatial factor of ~3